Apparatus for screening seed and the like materials

ABSTRACT

Seed screening apparatus having two vertically arranged screening drums suspended from vertical shafts which are supported by means of a main shaft, said main shaft being provided with driving means for rotating the main shaft and accordingly apply a planetary motion to the drum shafts during which planetary movement the drums rotate about their shafts, means being provided for creating a pressure outside the drums which is lower than the pressure prevailing inside the drums.

United States Patent [191 Rasmussen Oct. 23, 1973 [54] APPARATUS FORSCREENING SEED AND 1,344,921 6/1920 Meyer 209/28 X THE LIKE MATERIALS2,384,181 9/1945 La Fave. 209/28 X 2,804,976 9/1957 Russell 210/325 XInventor: Svend J g Rasmussen, Mlllinge, 2,880,734 4/1959 Edstrom....209/303 x Denmark 3,062,375 11/1902 Palm 209/303 [73] Assigneez DamasJens Nielsens Maskintabrik 3,092,582 6/1903 Lacken 233/7 X AI Vester y.Denmark FOREIGN PATENTS OR APPLICATIONS 22 Filed: t 12 1971 228,8991/1920 Great Britain 209/22 [2]] Appl' N07 188180 Primary ExaminerRobertHalper AttorneyWatson, Cole, Grindle & Watson [30] Foreign ApplicationPriority Data Oct. 12, 1970 Denmark 5158 57 ABSTRACT 52 U.S. Cl 209/240209/22 209 295 1 Seed Waning apparatus having vertically 209/303 rangedscreening drums suspended from vertical shafts [51] Int. Cl B07b 1/26which are Supported by means of a main shaft said 581 Field of Search209/303 291 295 main Shaft being Pmvided with driving means 209/24O 2122 233,2 6 tating themain shaft and accordingly apply a plane- 325 tarymotion to the drum shafts during which planetary movement the drumsrotate about their shafts, means [56] Reerences Cited being provided forcreating a ,pressure outside the drums which is lower than the pressureprevailing in- UNITED STATES PATENTS Side the drums 413,161 10/1889Beeman 209/295 X 978,178 11/1910 Thomas 210/325 1 Claim, 2 DrawingFigures PATENTEBBU 2 3 I973 SHEET 1 0F 2 INVENTOR BY q [26? I ga IATTORNEY APPARATUS FOR SCREENING SEED AND THE LIKE MATERIALS BACKGROUNDOF THE INVENTION The present invention relates to an apparatus forscreening seed and the like materials. By experiments with screeningapparatuses comprising at least one screening drum which is rotatableabout its own axis and which simultaneously rotates about a main axisand wherein at least two outlets are provided, viz. one for the finematerial expelled from the screening drum or drums and one for thecleaned seed, it has been discovered that the degree to which the seedwill be cleaned is not as high as theoretically expected. Suchexperiments have proved that the seed after the screening operationstill contains a great proportion of sand and other fine impurities. Onthe other hand, said experiments have proved that the particle sizeswhich are only a little smaller than the screen openings really areremoved from the screening material. In order to solve the problem withthe impurities in the cleaned seed a theory has been set up, viz. thatthe impurities remain in the cleaned seed due to a suction actioncreated in the outlet for the cleaned seed due to the high screeningrate of screening apparatuses constructed as mentioned above. Thistheory has been supported by the fact that the high screening ratenecessitates a high outlet rate of the cleaned seed, and accordingly thecleaned seed will carry a lot of air out through the outlet for thecleaned seed. If such removal of air from the screening drum or drumsincreases the amount of air admitted to the drum or drums togetherwiththe screening material a vacuum will be created in the drum or drumsand such vacuum will tend to prevent the expelling of the impuritiesfrom the drum or drums.

SUMMERY OF THE INVENTION According to the present invention means areprovided for creating a flow of air out through the screening drum ordrums. Experiments have shown that such a flow of air solves the problemreferred to above and removes the impurities from the cleaned seed dueto the fact that said flow of air will carry away the fine ma: terialwhich otherwise would pollute the cleaned seed.

Such a flow of air passing from the interior of the drum or drumsthrough the screening openings thereof and outwardly may be created inseveral different ways. E.g., an exhauster may be connected tothe outletfor the fine material. Another possibility consists in a freecommunication between the interior of the drum or drums and theatmosphere surrounding the apparatus because such precaution prevents avacuum from building up in the interior of the drum or drums. In orderto secure such a result the inlet to the apparatus for the screeningmaterial may according to the present invention be provided with an airby-pass duct which is kept free of screening material during the inflowthereof in such a way as to secure sufficient air admittance to theinterior of the drum or drums.

In case the apparatus is provided with a collecting channel arrangedcoaxially with the main axis for collecting the fine material expelledfrom the screening drum or drums and wherein vanes engage in order tomove the fine material to the outlet therefor and with a collectingchannel also arranged coaxially with the main axis for collecting thecleaned seed, and wherein vanes also engage in order to move the cleanedseed to the outlet therefor, the vanes for moving the fine material mayaccording to the present invention be shaped in such a way as to createa flow of air out through the outlet for the fine material which flow ofair is greater than the flow of air out through the outlet for thecleaned seed. In this embodiment the effect aimed at is achieved solelyby parts of the apparatus which are necessary for the working of theapparatus, viz., solely by forming the vanes for the fine material asfan wings. Experiments have shown that such shaping of the vanes resultsin the air flow conditions requested and explained above. This result is.due to the fact that the vanes for screening apparatuses constructed asstated above move along a circle having a great diameter, andaccordingly they are able to apply a considerable centrifugal action tothe air. On the other hand, it is of course neessary to avoid that thevanes which move the cleaned seed create the same air flow rate.However, this is easily achieved by a man skilled in the art on thebasis of the theory relating to centrifugal fans.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical section through apreferred embodiment for the screening apparatus according to theinvention, and 1 FIG. 2 is a horizontal section along the line II-II inFIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT.

The screening apparatus shown comprises a base 1 wherein a verticalshaft 2 is rotatably supported by means of a bearing In. Two pair ofcross arms 3,3a and 4,4a, respectively are secured to the shaft 2. Atthe end of the cross arms two vertical shafts 5 and 5a are rotatablysupported. A screening drum is suspended from each of the shafts 5,5a bymeans of arms 6 and 6a, respectively. Each screening drum consists of acylindrical outer screen plate 7 and 7a, respectively, and a cylindricalinner screen plate 8 and 8a, respectively. At the lower end of the shaft2 a V-pulley 2a is secured which by means of a driving belt (not shown)is connected to a motor (not shown) so as to rotate the main shaft 2. Bysuch rotation also the shafts 5 and 5a will be rotated via the arms 3,3aand 4,4a in such a way that the shafts 5 and 5a move in a planetarymovement about the shaft 2. To the lower end of each of the shafts 5 and5a a sprocket 30,30a, respectively is secured. Each of the sprockets30,301: is connected with a stationary sprocket 32,32a, respectively bymeans of a drive chain 31 and 31a, respectively. The stationarysprockets 32 and 320 are supported by means of a stationary sleeve 33through which the shaft 2 extends and which is supported by the bearingla in such a way that the shafts 5 and 5a rotate about their own axessimultaneously with the planetary movement about the main shaft 2.Moreover, the shaft 2 supports a hopper 9 having two outlets, viz. onefor each of the screening drums. The hopper 9 participates in theplanetary movement referred to above in such a way that screeningmaterial continuously are fed to the screening drums.

Moreover, the shaft 2 carries a plate lo wherein an outlet arrangementis suspended below each screening drum. Each outlet arrangement consistsof an outer cylinder 11 and lla,respectively, the diameter of whichcorresponds to the diameter of the outer screen plate 7 and 7a,respectively and of a sloping bottom 14 and 14a, respectively. Thesloping bottoms 12,120 and 14,14a project over collecting channels 15and 16, respectively. Each of the channels has a tangential outlet 17and 18, respectively and vanes 19 and 20, respectively project into thecollecting channels in order to transport the materials out through theoutlets. To the periphery of the plate 10 vanes 21 are secured whichproject into a collecting channel 22 to which a tangential outlet 23 isconnected. The collecting channels 15,16 and 22 are arranged along theinner surface of a housing 24 which encloses the apparatus and extendscoaxially with the centre shaft 2. The housing 24 comprises a slopingroof 25 which ends in a downwardly extending collar 26 which surrounds afeeding opening. The collar 26 projects into an upwardly facing openingin the hpper 9. In the opening defined by the collar 26 an inlet tube 27for screening material is secured by means of struts 26a. The tube 27has a diameter less than the diameter of the collar 26 so that a spaceis provided for inflowing air as indicated by the arrow 28. By means ofstruts 27a an upper bearing 1b for the shaft 2 issecured to the tube 27.This construction assures that, simultaneously with feeding screeningmaterial to the apparatus as indicated by means of the arrow 29, anample flow of air will be admitted to theinterior of the screening drumsthrough the hopper 9.

The screening apparatus illustrated operates as follows:

The material supplied to the hopper 9 is introduced into the spacingsformed by the inner screen plates 8 and 8a. A combined centrifugalforcewill be applied to such material partly due to the rotation of thescreening drums about the shafts and 5a and partly due to the planetarymovement of the shaft 5 and 5a and accordingly also the drums about theshaft 2. This combined centrifugal force results in a screening of thematerial through the inner screen plates 8 and 8a. The material which isunable to pass through the inner screen plates will due to the gravityforce be moved down through the cylinders 13 and" 13a, over the slopingbottoms 14,14a thereof and out into the collecting channel from whichthe material will be conducted out through the outlet 18 by means of thevanes 20. The material which 'passes the screen plates 8 and 8a will bescreened once more by means of the outer screen plates 7 and 7a, and thematerial which does not pass out through, the outer screen plates,thecleaned seed, will pass through the cylinders 11 and 11a, over thesloping bottoms l2 and 12a thereof and down into the collecting channelfrom which the material is removed by means of the vanes 19 out throughthe outlet 17. The fine material will pass out through the outer screenplates 7 and 7a and be collected in the channel 22 from which thematerial is removed by means of the vanes 21 through the outlet 23.

The screening apparatus shown and explained above has a very highscreening rate and accordingly it is necessary to secure a high outletrate of the cleaned seed. No matter how the removal arrangement for thecleaned seed is arranged the flow rate of cleaned seed will be ratherhigh and accordingly a great amount of air will be carried away togetherwith the cleaned seed removed. Accordingly, a risk exists that a partialvacuum will be created in the interior of the screening drums. If suchvacuum really is created, it will be difficult for the fine material tobe expelled out through the screening drums. Accordingly, precautionshave been taken in order to secure a flow of air from the interior ofthe screening drums and outwardly therefrom through the screeningopenings. In the embodiment shown, an ample air admission to theinterior of the apparatus is secured by means of the positioning of theair inlet tube 27 as explained above. Moreover, precautions have beentaken in order to create a suction effect in the collecting channel 22through which the fine material is removed and which accordinglycommunicates with the outer surfaces of the screening drums. The latterprecautions consist in that the vanes 21 are arranged closely adjacenteach other and have a curved shape in the same way as fan wings for acentrifugal fan, cf. FIG. 2. This is a very simple embodiment due to thefact that the vanes 21 must be provided in order to remove the finematerial in the embodiment shown on the drawing. Due to the fact thatthey are arranged along the periphery of the plate 10 they will movealong a circular path having a great diameter, and accordingly they willoffer a considerable action upon the air in the collecting channel 22.In order to further support the suction effect achieved thereby thecollecting channel 22 may be shaped as a spiral housing havingincreasing width in the circumferential direction towards the outlet 23.A further possibility for achieving the flow of air referred to above inconnection with this and other embodiments of the present inventionconsists in connecting an exhauster (not shown) to the outlet 23 for thefine material.

Moreover, by the embodiment shown on the drawing precautions have beentaken in order to avoid a too heavy suction action in the collectingchannel '15 for the cleaned seed and in the collecting channel for thecoarser material. These precautions consist in that the amount and shapeof the vanes 19 and 20 working in the channels 15 and 16 have beenselected in such a way that the removal of the materials is carriedoutwithout dragging too much air out through the outlets 17 and 18 togetherwith the materials. Accordingly, it is secured that a pressure prevailsalong the outer surface of the screening drums inside the housing 24above the plate 10 which is less than the pressures prevailing insidethe screening drums and accordingly a flow of air as explained above issecured for carrying the fine material out through the outer screenplates 7 and 7a.

Iclaim: I

1. Apparatus for screening seed'particles and the like, comprising astationary outer housing, a vertical central shaft rotatably supportedin said housing, at least'two vertical planetary shafts supported bysaid central shaft, screening drums rotatably supported within saidhousing on each of said planetary shafts coaxially with said respectiveplanetary shafts, each of said drums comprising at least an innermostand an outermost coaxially arranged screen, driving means rotat ing saiddrums about said central shaft and simultaneously rotating saidscreening drums on said planetary shafts, a hopper provided with anumber of outlets corresponding to the number of screening drums, eachsaid outlet communicating with the interior of the innermost screen ofeach drum through the open ends thereof, an inlet tube for material tobe screened being positioned at the top of said housing andcommunicating with the interior of said hopper, an air by-pass openingwhich opens into the outer atmosphere and into the interior of saidh0pper surrounding said inlet collecting channel being secured to saidduct means mounted on said central shaft communicating with said secondcollecting channel, a third collecting channel supported by said housingand communicating with the exterior of said drums, still other vanemeans projecting into said third collecting channel being distributedalong the full circumference of a plate secured to said central shaftand supporting said duct means said other vane means being curved andclosely adjacent each other.

=l= l t

1. Apparatus for screening seed particles and the like, comprising astationary outer housing, a vertical central shaft rotatably supportedin said housing, at least two vertical planetary shafts supported bysaid central shaft, screening drums rotatably supported within saidhousing on each of said planetary shafts coaxially with said respectiveplanetary shafts, each of said drums comprising at least an innermostand an outermost coaxially arranged screen, driving means rotating saiddrums about said central shaft and simultaneously rotating saidscreening drums on said planetary shafts, a hopper provided with anumber of outlets corresponding to the number of screening drums, eachsaid outlet communicating with the interior of the innermost screen ofeach drum through the open ends thereof, an inlet tube for material tobe screened being positioned at the top of said housing andcommunicating with the interior of said hopper, an air by-pass openingwhich opens into the outer atmosphere and into the interior of saidhopper surrounding said inlet tube, a first collecting channel supportedby said housing below said drums and communicating via duct meansmounted on said central shaft with the interior of the innermost screensof said drums, vane means projecting into said first collecting channelbeing secured to said duct means communicating with said firstcollecting channel, a second collecting channel supported by saidhousing below said drums and communicating via other duct means mountedon said central shaft with the spacings between the screens of saiddrums, other vane means projecting into said second collecting channelbeing secured to said duct means mounted on said central shaftcommunicating with said second collecting channel, a third collectingchannel supported by said housing and communicating with the exterior ofsaid drums, still other vane means proJecting into said third collectingchannel being distributed along the full circumference of a platesecured to said central shaft and supporting said duct means said othervane means being curved and closely adjacent each other.